Deicing system



March 16, 1965 5. J. JUSYK 3,173,491

' DEICING SYSTEM Filed Nov. 21, 1963 2 Sheets-Sheet. 1

F/iZ Z/u March 16, 1965 5. J. JUSYK 3,173,491

DEICING SYSTEM Filed Nov. 21, 1963 2 Sheets-Sheet 2 United States Patent 'ice 3,173,491 DEICING SYSTEM Stanley J. Jusyk, Southport, Conn., assignor to United Aircraft Corporation, East Hartford, Conn., a corporation of Delaware Filed Nov. 21, 1963, Ser. No. 325,219 11 Claims. (Cl. 170159) This invention relates to a rotor blade deicing system using an aerodynamic discontinuity principle in combination with contrahesive material.

An object of this invention is to shed ice by centrifugal force acting upon a mass of ice which is adhering to a low coefficient of friction material with a minimized chordwise bearing surface area.

Another object of this invention is to provide an ADP member or tape which can be fixed to a rotor blade to form the minimized bearing surface area having a step or discontinuity on the lower surface of the blade.

A further object of this invention is to provide a light weight means which will deice a rotating rotor blade.

Another object of this invention is to provide a limited area for ice accretion on a low ice adhesion surface, said area being rotated so that ice removal depends on centrifugal force.

A further object of this invention is to provide a deicing system which can be easily adapted to existing rotor blades and easily maintained.

Another object of this invention is to provide a deicing system which will not adversely affect blade performance.

A further object of this invention is to provide a contrahesive material for the ADP tape.

Another object of this invention is to provide an ADP tape which has the heighth of its step increased as it extends inwardly from the tip of the blade and has its chordwise lentgh reduced as it extends in the same direction.

Other objects and advantages will be apparent from the specification and claims and from the accompanying drawings which illustrate an embodiment of the invention.

FIGURE 1 is a top view of a rotor blade with a section removed showing an ADP member or tape applied thereto.

FIGURE 2 is a view showing a cross section through the ADP member or tape before application on a blade.

FIGURE 3 is a cross-sectional view taken on line 3-3 of FIG. 1 showing the ADP member or tape positioned on the leading edge of a rotor blade.

FIGURE 4 is a bottom view of a rotor blade with a section removed showing a modified ADP member or tape applied thereto.

FIGURE 5 is a cross-sectional view taken on the line 5-5 of FIG. 4.

FIGURE 6 is a cross-sectional view taken on the line 6--6 of FIG. 4.

FIGURE 7 is a cross-sectional view taken on the line 7-7 of FIG. 4.

With reference to FIG. 1, one type of rotor blade is shown in US. Patent No. 2,754,917 to R. M. Kee. The blade 2 shown therein consists essentially of an extruded metal spar member 10 which extends from the root to the tip of the blade and comprises the main strength member as well as the leading portion of the blade. This spar forms a substantial chordwise portion of the blade and conforms to the airfoil contour thereof. The remainder of the chordwise extent of the blade is made up of V-shaped metal pockets or boxes 12, the forward parts of which are secured to the rearward part of the spar member. While this specific construction has been described, it is to be understood that the blade construction is not part of this invention.

Covering a portion of the leading edge of the blade 2 3,173,4isi

Patented Mar. 16, 1965 is an ADP member or tape 20. The abbreviation ADP where it appears refers to aerodynamic discontinuity principle. Further, the term contrahesive in the specification refers to those materials which have lower adhesion-to-ice characteristics. This member 20 extends from the leading edge of the airfoil section of the blade to a line under the blade, where it ends in a step 22, to a line over the blade where it blends into the contour of the blade.

If a flexible ADP tape is used, it can be placed on a roll and the needed length unrolled as necessary. If a more rigid tape is used, such as even a metal, it can be made of a specific length having the cross section indicated in FIG. 2 and then prebent or formed to a known shape for use on a specific blade airfoil. While a blade having a symmetrical airfoil is shown, this invention may be used on blades having other airfoil sections. In this regard, it is only necessary to know the variation of the stagnation point or line in normal operation of the aircraft. This will determine the location of the bottom end position of the ADP tape since it should extend approximately of an inch along the airfoil contour downstream of the lower stagnation point or line limit. The location of the top end position of the ADP tape can be at any point where the tape can blend with the airfoil and interfere the least with the intended function of the original airfoil.

In FIGS. 1-3, a constant thickness tape is shown which provides a step of constant height extending along the length of the blade at substantially a constant distance from the leading edge.

The basic principle of the ADP tape deicing system is the utilization of centrifugal force available from the rotating rotor blades to shed ice. The ice resists this shedding by adhering to the blade. In order to enhance shedding, first, the area of ice deposition is reduced in making use of the discontinuity principle, and second, the area of impingement is covered by a contrahesive material. The discontinuity principle is a name applied to the controlled ice deposition on a blade due to a discontinuity or step in the underside of a blade airfoil section. As can be seen in FIG. 3, this step is caused by the application of the deicing tape, and while the step is formed on the lower side of the air foil, the upper portion is leveled so as to blend in with the airfoil. The heighth of the step is determined by tape thickness; this plus the location of the tape on the blade provides a controlled catch area for ice deposition.

Gontrahesive materials, those materials which have low adhesion-to-ice characteristics can vary with the amount of shedding which is to be desired. In successful tests made, a Fiberglas tape impregnated with Tefion and a polyethylene tape were used. These tapes were of 10 mils and 12 mils (.010 and .012 inch) in thickness respectively. Tests indicate that the thickness of a tape having a constant step heighth and a constant chordwise extension on the bottom of the blade from the step to the leading edge of the blade can vary with chord length, and for chord lengths of from 7-19 inches should not go above 20 mils and not go below approximately 6 mils.

While larger steps have been formed in stationary airfoil surfaces to remove moisture, this teaching would not be applicable to a rotary wing having a varying pitch angle and which provides a lifting action.

For a symmetrical airfoil section (NACA .0012) having a 16.4 inch chord, a tape of a constant 10 mil thickness was placed on the blade so that it extended of an inch below the underside of the blade from the leading edge forming a Step at its end (see FIG. 3) while it extended 1% inches along the top of the blade where it blended into the section.

With reference to FIGS. 4-7, a modification of the ADP member or tape is shown. In this configuration, the member or tape 20a has the heighth of its step increased as it extends from the outboard end of the blade towards the inboard end, and further, the chordwise length from the leading edge of the member, or tape, 20a on the bottom of the blade is reduced as it extends inwardly from the outboard end of the blade. This chordwise length while it decreases always extends to a point which permits the lower stagnation line limit to fall on the member, or tape, 20a.

The member or tape is fabricated in this manner to take into consideration the reduced velocity of points along the blade as the blade extends inwardly from the tip to the root. In a like manner, the centrifugal force acting at the different points will also be decreased as the points extend inwardly along the blade. The reduced velocity at the inboard points permits the Step 22a to be larger near the root end and not greatly affect the performance of the blade. The reduction in bearing surface of the contrahesive material reduces the amount of ice which has to be shed which is desirable because of the lower centrifugal force at the inboard points.

A representative blade having an airfoil section of NACA .0012 and with a chord of approximately 18 inches could have a tape of this nature with its stepped end extending from a point approximately at a 100% span about of an inch behind the leading edge to a point at a 20% span which is of an inch from the leading edge. The thickness of the step could vary from 8 mils at the 100% span position to around 35 mils at the 20% span position.

It is to be understood that the invention is not limited to the specific description above or other specific figures, but may be used in other ways without departure from its spirit as defined by the following claims.

I claim:

1. A blade subject to centrifugal force along its length having a strip material covering a portion of the length of the forward end of said blade to form a limited chord- Wise extending area for ice accretion, said strip material extending under the blade for a distance covering the limits of movement of the stagnation point in normal operation of the blade, the strip material being contrahesive, the end of said strip material under the blade forming a step, the end of said strip material over the blade blending in with said blade.

2. A blade having a lower and upper surface subject to centrifugal force along its length, a tape covering a substantial spanwise portion of the length of the forward end of said blade to form a limited chordwise extending area for ice accretion, said tape extending under the blade for a distance covering the limits of movement of the stagnation point in normal operation of the blade, the material of said tape being contrahesive, the end of said tape under the blade forming a relatively blunt discontinuity in the lower surface of said blade, the end of said strip material over the blade blending in with said blade.

3. A blade subject to centrifugal force along its length, a tape covering a portion of the length of the forward end of said blade to form a limited chordwise extending area for ice accretion, said tape extending under the blade for a distance covering the limits of movement of the stagnation point in normal operation of the blade,

the material of said tape being contrahesive, the end of said tape under the blade forming a step, the end of said tape over the blade blending in with said blade.

4. A blade subject to centrifugal force along its length, a metallic strip member covering a portion of the length of the forward end of said blade to form a limited chordwise extending area for ice accretion, said metallic strip member extending under the blade for a distance covering the limits of movement of the stagnation point in normal operation of the blade, the material of said metallic strip member being contrahesive, the end of said metallic strip 4 member under the blade forming a step, the end of said metallic strip member over the blade blending in with said blade to interfere the least with the airflow over the blade.

5. A blade having a chord line in the range of 7-19 inches subject to centrifugal force along its length, a strip member covering a portion of the length of the forward end of said blade to form a limited chordwise extending area for ice accretion, said strip member extending under the blade for approximately A; of an inch covering the limits of movement of the stagnation point in normal operation of the blade, the material of said strip member being contrahesive, the end of said strip member under the blade forming a step, the end of said strip member over the blade blending in with said blade.

6. A blade having a chord line in the range of 7-19 inches subject to centrifugal force along its length, a strip member covering a portion of the length of the forward end of said blade to form a limited chordwise extending area for ice accretion, said strip member being in the range of from 8 mils to 20 mils thick, said strip member extending under the blade for a distance covering the limits of movement of the stagnation point in normal operation of the blade, the material of said strip member being contrahesive, the end of said strip member under the blade forming a step the end of said strip member over the blade blending in with said blade.

7. A blade having a chord line in the range of 7-19 inches subject to centrifugal force along its length, a strip member covering a portion of the length of the forward end of said blade to form a limited chordwise extending area for ice accretion, said strip member being in the range of from 8 mils to 20 mils thick, said strip member extending under the blade for approximately M; of an inch covering the limits of movement of the stagnation point in normal operation of the blade, the material of said strip member being contrahesive, the end of said strip member under the blade forming a step, the end of said strip member over the blade blending in with said blade.

8. An airfoil having longitudinally extending major upper and lower airfoil surfaces connected to form a leading edge and a contrahesive material covering a substantially spanwise portion of said major surfaces and extending around said leading edge, said material extending from said leading edge in a chordwise direction along said lower surface to a first line aft of the chordwise region of the stagnation line of the airstream during normal operation, said first line being at the trailing edge of said material with said edge forming a relatively blunt discontinuity of said lower surface said material extending from said leading edge in a chordwise direction over said upper surface to a line where it blends in with said blade.

9. A blade for use on a rotating rotor head including, a strip member covering a substantial portion of the length of the forward end of said blade to form a limited chordwise extending area for ice accretion, said strip member extending under the blade for a distance covering the limits of movement of the stagnation point in normal operation of the blade, the end of said strip member under the blade forming a step, the end of said strip member under the blade forming a taper with the forward end of the blade so that the strip member decreases in chordwise length with respect to its forward end as it extends inwardly from the outboard end of the blade, the end of said strip member over the blade blending in with said blade.

10. A blade for use on a rotating rotor head including, a strip member covering a substantial portion of the length of the forward end of said blade to form a limited chordwise extending area for ice accretion, said strip member extending under the blade for a distance covering the limits of movement of the stagnation point in normal operation of the blade, the end of said strip memher under the blade forming a step, the end of said strip member under the blade forming a taper with the forward end of the blade so that the strip member decreases in chordwise length with respect to its forward end as it extends inwardly from the outbord end of the blade, the end of said strip member over the blade blending in with said blade, the thickness of the end of the strip member increasing as it extends inwardly from the outboard end of the blade.

11. A blade for use on a rotating rotor head including, a strip member covering a substantial portion of the length of the forward end of said blade to form a limited chordwise extending area for ice accretion, said strip member extending under the blade for a distance covering the limits of movement of the stagnation point in normal operation of the blade, the end of said strip member under the blade forming a step, the end of said strip member under the blade forming a taper with the forward end of the blade so that the strip member decreases in chordwise length with respect to its forward end as it References Cited by the Examiner UNITED STATES PATENTS 2,385,662 9/45 Vonnegut 244134 2,617,269 11/52 Smith Johannsen 244-434 2,809,130 10/57 Rappaport 170159 2,997,229 8/61 Quan 244134 X FOREIGN PATENTS 662,110 11/51 Great Britain.

JULIUS E. WEST, Primary Examiner.

EDGAR w. GEOGHEGAN, Examiner. 

1. A BLADE SUBJECT TO CENTRIFUGAL FORCE ALONG ITS LENGTH HAVING A STRIP MATERIAL COVERING A PORTION OF THE LENGTH OF THE FORWARD END OF SAID BLADE TO FORM A LIMITED CHORDWISE EXTENDING AREA FOR ICE ACCRETION, SAID STRIP MATERIAL EXTENDING UNDER THE BLADE FOR A DISTANCE COVERING THE LIMITS OF MOVEMENT OF THE STAGNATION POINT IN NORMAL OPERATION OF THE BLADE, THE STRIP MATERIAL BEING CONTRAHESIVE, THE END OF SAID STRIP MATERIAL UNDER THE BLADE FORMING A STEP, THE END OF SAID STRIP MATERIAL OVER THE BLADE BLENDING IN WITH SAID BLADE. 